Income Taxes (Details) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Income Taxes
Deferred tax benefit	$ 2,600,000	$ 5,600,000	$ 1,100,000
Goodwill impairment	57,213,000	57,213,000
U.S. statutory rate		34.00%
Net deferred tax liability	49,226,000	49,226,000		55,603,000
Deferred tax liability related to the basis differences of the properties, plant and equipment	64,000,000	64,000,000		65,500,000
Deferred tax asset related to Mexico net operating losses	14,900,000	14,900,000		10,100,000
Unrecognized tax benefits	$ 2,600,000	$ 2,600,000		$ 2,700,000